In a CDMA2000 1× EV-DO network, a radio link between an access terminal (AT) and an access network (AN) mainly has the following several states: an initialization state, an idle state, and a connected state. The initialization state means a process in which the AT finds a network after startup and is synchronized to the network. The connected state means that an open connection exists between the AT and the AN, and forward and backward data packet transmission and receiving may be performed. The idle state means a state after the AT is synchronized to the network and before a connection is established. In the idle state, the AN sends a paging message for the AT, and AT monitors a control channel message, paging, and the like, to prepare for service connection establishment that may be initiated at any time. A synchronous capsule (SC), a sub-synchronous capsule (SSC), a synchronous sleep state capsule, and an asynchronous capsule may be transferred on a control channel, and the synchronous sleep state capsule may be carried in the SC or the SSC for transfer.
The AT in the idle state generally has the following several sub-states:
1. A non-activated state: When the AT has captured a service network but a connection is not opened, the AT is in a non-activated state. In this state, the AT waits for an ACTIVE command, and the AT continuously monitors the control channel.
2. A monitoring state: When there is no data transmission in the connected state, the AT sends a disconnection message to the AN, and then the AT enters a monitoring state. In this state, the AT continuously monitors the control channel, and monitors a paging channel, and when necessary, updates a parameter received on the control channel, and the AN may send paging for the AT, and the AT monitors the paging and responds to the paging.
3. A sleep state: When receiving a synchronous sleep state capsule, the AT enters a sleep state. The AT closes some processing resources to reduce power consumption and lengthen a battery life. In this state, the AT does not monitor the control channel, and does not allow the AN to send a unicast packet to the AT.
4. A connection establishment state: When the AT in the idle state has data to send, the AT and the AN establish a connection. In this state, the AT continuously monitors the control channel.
It can be known from above that, when being in other states than the sleep state, the AT needs to enable a radio frequency module all the time to continuously monitor the control channel, to receive a message transferred on the control channel. Specifically, referring to FIG. 1, FIG. 1 is a sequence chart showing that an access terminal monitors a control channel in a conventional technology. In FIG. 1, when being in a sleep state, the AT does not monitor the control channel, and therefore, does not receive a message transferred on the control channel. When the AT is in other states than the sleep state, the AT needs to continuously monitor the control channel, to receive a message transferred on the control channel. The AT is in other states than the sleep state most of the time. Consequently, continuous monitoring the control channel increases power consumption.